mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

, in the field of topology, a topological space is said to be pseudonormal if given two disjoint

closed set In geometry, topology, and related branches of mathematics, a closed set is a set whose complement is an open set. In a topological space, a closed set can be defined as a set which contains all its limit points. In a complete metric space, a cl ...

s in it, one of which is countable, there are disjoint open sets containing them. Note the following: * Every normal space is pseudonormal. * Every pseudonormal space is regular. An example of a pseudonormal Moore space that is not metrizable was given by , in connection with the conjecture that all normal Moore spaces are metrizable..

References

Topology Properties of topological spaces {{topology-stub